Well, usually, if you have reached the point of having called a tow truck, then the police have become involved, an accident report has or is being filed and no doubt fault-unless it is an extreme case in which it is uncertain or someone is desperatly trying to argue the case, then fault has been determined. Whomever is at fault will have to pay to have a car towed. The towing process would then lead to the auto garage where the damage would be accessed and repairs rendered, the final bill which would of course include the towing, would be then handed to the one At Fault, along with the towing fees and repairs to their own vehicle. Insurance would no doubt cover some of this whole mess but of course rates would go up due to the accident.